In the manufacture of articles of glass or other materials it is necessary to dose portions of molten glass for the formation of the articles.
These portions of molten glass are obtained from a source of molten glass which has a doser which comprises one or more orifices, usually two or four, each of which simultaneously supplies a jet of molten glass which is cut by suitable knives into portions known as gobs.
These gobs are distributed by a gob distributor through stationary channels to the cavities of the individual molding sections (customarily eight) of the machine in order to produce articles of glass of the "I.S. Machine" type.
The gob distributors are apparatus formed of curved distributor scoops (the number of which depends on the number of orifices of the doser and/or the number of cavities and sections of the machine) which are moved simultaneously towards or into gob receiving positions and towards gob delivery positions which coincide with the positions of the upper ends of the respective fixed channels.
The fixed channels (the number of which depends on the number of orifices of the doser multiplied by the number of sections of the machine) are fastened on the machine and arranged in a semi-circular configuration in such a manner that their upper ends coincide towards a point close to the doser, in coincidence with the curved distributor scoops, and their lower ends terminate close to or at the entrance of the cavities of the respective sections of the machine.
Gob distributors are well-known in the art and have achieved a very efficient stage of development during the last few years, so that they are extremely efficient units which make it possible to shape articles of glass in machines having multiple cavities and sections, which has increased production capacity and quantity to a great extent.
The gob distributors most recently known in the art consist generally of one or more curved distributor scoops whose upper end is located at any time below the orifices of the doser and whose lower end turns angularly to selective gob entrance positions which coincide with the positions of the upper ends of the aforementioned fixed channels.
For example, U.S. Pat. No. 3,597,187 to Urban P. Thrudeau and its reissue, U.S. Pat. No. Re. 28,073 granted on Aug. 3, 1971, and July 9, 1974, respectively and assigned to Owens-Illinois, Inc., describes a gob distributor in which each of the curved distributor scoops is supported individually by a vertical shaft which has a pinion at its lower end meshing with a rack of sector shape supported on a vertical shaft which has a cam follower which is compelled to follow the path of a cam in order to move the rack and pinion assembly sequentially so as to turn the scoops into predetermined delivery positions. Said cam is caused to rotate continuously by a drive mechanism which consists of a transverse shaft coupled at one end to the cam and which at its other end has a gear which meshes with a worm which is turned by a motor synchronized with the operating controls of the machine, such as the well-known time drum.
Due to their design and arrangement, these gob distributors have become more and more complicated, even including additional scoops for machines with sections of multiple cavities, for instance four, resulting in problems with respect to distribution, space and maintenance.
In U.S. Pat. No. 3,721,544 to Wasyl Brytrianyk and Francis A. Sarkozy, granted on Mar. 20, 1973 and assigned to Emhart Corporation there is described a gob distributor which comprises essentially a pair of rotary curved distributor scoops; a mechanism for supporting said scoops in a dependent linear relationship in order to cause then to turn on each of their vertical shafts, which mechanism includes a ring spur gear coupled to the upper end of each scoop and a funnel portion on the gear; a horizontally extending slideable member supported in a box which supports the mechanism and which at one of its ends has a rack portion which meshes with the spur gears of the upper part of the scoops in order to turn them by reciprocatable movements thereof and at its opposite end a rotary cam follower having a plurality of lobes, each of which has a predetermined lift which produces a reciprocating movement which defines the positions at which the distributor scoops turn to their selective delivery positions.
Finally, U.S. Pat. No. 3,775,083 to Nevelung et al., granted on Nov. 27, 1973, and assigned to Emhart Corporation describes a gob distributor having an arrangement of scoops similar to that of the preceding patent, which varies as to the manner of controlling the movement of the mechanism for supporting the scoops, which is obtained by means of racks on both sides of the ring spur gears coupled to the upper part of the scoops, each of which racks is actuated in reciprocation by fluid-operated motors in order to turn said ring spur gears and thereby the scoops in accordance with a sequence determined by signals or pulses fed to the linear motors.
These last two types of distributors require a cooling system both for the bronze bushings in which the gears are mounted and for the funnel portion, as well as for the scoops.
These cooling systems consist of passages of spiral configuration surrounding the funnel portion of the scoops and between the bushings and the gears. The cooling fluid generally used is water. These two last-mentioned patents to Bystrianyk and Nevelung have an advantage to the present to Thrudeau with respect to the solution of the problem of the distribution or arrangement of more than two curved distributing scoops since in these two last-mentioned patents said scoops are arranged in a line, fastened by gear-holding bushings to a supporting and cooling frame or housing.
Now it has been found that if the gobs of glass have the least possible contact with the parts of the machine during their feed path to it, the speed of passage reached by these gobs will be higher and the heat equilibrium reached for them better, which is highly desirable since with a higher speed of feed it is possible to increase the production and/or quality of the products produced.
In this respect, although the drop distributor of the Thrudeau patents has the problem of distribution or arrangement of the distributor scoops, it has the advantage of reducing the contact of the gob with the parts of the machine over the Bystrianyk and Nevelung distributors since the last two require bronze bushings, ring spur gears and a funnel portion which considerably increase the length of contact and the contact of said gobs with said parts, which reduces the speed of feed and the heat equilibrium of the drops, which is highly undesirable.
Furthermore said parts (bushings, gears and funnel portion) suffer considerable wear which cannot be compensated for automatically and they must be cooled with water by complicated systems which make the manufacture, assembly and maintenance thereof difficult, resulting in a higher cost, which makes the production and product more expensive.
In the distributors of Bystrianyk and Nevelung it is furthermore necessary to use gob rejectors which are mechanisms which withdraw the distributing scoops or put in position extra channels in order to reject or conduct the gobs to a deposit of scrap (called "cullet") when it is not desired to feed gobs to the machine because of repair, cleaning or changing of molds.
By the gob distributor of the present invention all the distribution problems of the distributor scoops are solved, such as excessive wear of the parts of the distributor resulting in misadjustments which cannot be automatically compensated for, excessive contact of the gob with the parts of the distributor, the necessity of complicated and costly cooling systems, and the necessity of complicated rejector mechanisms due to the fact that the distributor scoops are connected directly in line to the drive and auxiliary arms and due to their "scissor-like" play, compensate for or automatically adjust the maladjustments in their articulated parts retaining their synchronism with the machine, and that they are easily cooled by air applied to the housing frame which supports them, without the necessity of bushings and gears which have to be cooled internally, whereby contact of the gob with said undesirable parts is avoided. (See page 11, lines 23-25 and page 12, lines 1-7 of Mexican text.)
As for the problems resulting from the use of cams as drive elements for effecting the sequence of movements which is required in the distribution scoops of the gob distributor, they are well-known and reside essentially in the fact that as the cam is used as a drive element, as is clearly described in the afore-mentioned U.S. patents to Trudeau and Bystrianyk et al., these cams suffer considerable wear by virtue of the fact that they are continuously exerting substantial forces in order to move the entire mechanism at high speed so that their cam surface is rapidly damaged and the distribution scoops start to become misadjusted in their movements, a moment being reached when it is necessary to stop the machine in order to replace the cam in question since the variation in position caused by the wear of the surface of the cam has the result that the distribution of the gobs of glass becomes inefficient within a short time. Furthermore, drive cam mechanisms like those previously indicated have the great disadvantage that it is necessary to provide frequent and careful maintenance of the stationary channels for the reception of gobs of glass corresponding to each of the molding selections since if the distributing scoops and/or the stationary channels become slightly out of line the distribution of the gobs of glass to the different sections of the machine also becomes inefficient in the case of such slight misalignment of the channels and scoops. Furthermore, these mechanisms which are operated by drive cam necessarily require a motor which operates in strict synchronism with the time drum of the glass article molding machine since if the motor slows down or goes faster there is no way of correcting it unless the machine is stopped and the indicated repairs are made.
Another important disadvantage of mechanical controls by drive cam for gob distributors resides in the fact that as said controls are based on a mechanical cam there is absolutely no possibility of modifying, if desired, the sequence of operation of the different sections of a machine for the molding of glass articles unless the cam is replaced by another entirely different one which contains said sequence, and this, of course, can only be done after stopping the machine in order to effect the replacement of the cam, a mechanical operation which in itself is complicated in view of the act that the cam is normally covered and it is necessary to remove a large number of parts in order to effect its replacement. Finally, with these drive cam mechanisms it is necessary, in the event that it is not desired that the gobs of glass pass to one or more sections of the machine which may be under repair or in which the molds are being changed or similar operations carried out, to operate a gob rejector entirely separately and by completely different controls which must be operated by entirely different fluid or mechanical signals, which constitutes another serious disadvantage of this type of drive cam mechanism.
Although the control mechanism of Nevelung et al., U.S. Pat. No. 3,775,083, completely eliminates the use of a drive cam to control the movement of the movable scoops of the distributor, it incorporates in its place a considerable complexity in the mechanism since it requires the provision and construction of a plurality of individual pistons, all located in tandem and some striking against others in a predetermined sequence in order to produce the staggered sequential movements of the distribution scoop so that this complexity in the mechanism results in continuous failures and has the result that said fluid controls is also highly ineffective, particularly for work at high speed.
In this particular case also an additional signal is required from the different molding stations of the glass article molding machine in order to insert the rejector in the event that one of said sections is under repair or the molds are being changed.
In this respect, co-pending Mexican Application No. 181,707 assigned to the same assignee as the present application, describes and claims an electronic gob distributor as well as a control system for same in which each of the distributing scoop is mounted on a shaft which is driven directly or indirectly by an individual pulse motor for each shaft or one pulse motor for all the shafts and an electronic control for the motors, by which is it possible to make the actuating shafts independent so as to control each one of the scoops in order to obtain optimum precision and flexibility, or the actuation of the channels jointly is permitted with high flexibility of adjustment, correction and sequence, and no mechanical or hydraulic means are employed to effect the control of movements, thus solving the problems of wear, synchronism and misadjustment inherent in the distributors of Thrudeau, Bystrianyk and Nevelung.
Now then, although the gob distributor of the present invention can use the same mechanical drive systems based on cams as its positioner to impart the movements of advance and retraction to the drive crank-holder arm for the actuation of the scoops it is also advisable to use the electronic drive system of the said Mexican Patent Application No. 181,707 as well as its electronic control systems as the positioner of the gob distributor of the present invention.
The manufacturers of stepping motors recommend, however, that they operate at higher speeds, above a resonance parameter at which synchronism could be lost, that is to say if the motors are operated at a given time at low speeds within the resonance parameter specified by the manufacturer, they may gain or lose pulses, each of which pulses is equivalent to approximately 0.001 inch, which, in cases such as the machining of a work part by a milling machine, is unimportant since said parts tolerate up to .+-.0.003 inch of error in their final machined measurements but in cases such as the gob distributor with which we are concerned is of great significance since the space present between the upper ends of the fixed channels, with which the dosing scoops coincide, is very small and critical and a gradual loss or gain of pulses will signify a lack of adjustment in the coincidence of the dosing scoops and the fixed channels and loss of synchronism with the rest of the machine.
In view of the foregoing, in cases in which one operates at high speeds and with critical precision, as in the case with which we are concerned, the manufacturers of these motors recommend that they not be stopped but that they be operated continuously and that only the high speeds be varied, that is to say that only gear transmissions be changed.
In order to avoid these problems of lack of synchronization of the pulse motors, the co-pending Mexican Patent Application No. 184,523 assigned to the same assignee as the present application, describes and claims a precision positioning system with desired programmed times in which use is made of two pulses motors which turn in opposite directions, connected to a rotating differential housing which rotates precisely and regularly due to changes in the speeds of its motors, which differential housing transmits its pulse to a positioner formed of a rack and pinion or a connection rod and fork, etc., thus eliminating the danger of operating the pulse motors at low speeds, within their resonance parameters, whenever both of its motors are operating jointly at high speeds and the only thing which varies is the speed of them within said range of high speeds which remain well above the resonance parameters which the manufacturers of pulse motors specify.
It is therefore highly advisable to use said precision positioning system with programmed desired times to actuate the gob distributor of the present invention.
From what has been stated above, it is obvious that the gob distributor of the present invention can be actuated with any type of positioner, whether mechanical or electronic, provided that the pulse or actuation is imparted to it in a synchronized and precise manner.